25.6.2013 Pressing & Sintering

Machinability Enhancement of PM Stainless Steels Using Easy-Machinable Stainless Steel Powder

PM stainless steels present very different machinability behaviors from plain carbon and low alloy PM steels. Since they contain high alloy content without carbon addition, stainless steels become gummy and work harden during machining so that they are difficult to machine. To improve the machinability, conventional machinability enhancers such as MnS and MoS2, etc. may be applied into the materials but the sulfur containing additives can severely decrease corrosion resistance. Resin-impregnation is also a common solution for improving the machinability of stainless steel materials without detrimental effect on corrosion resistance. However, resin impregnation not only greatly increases operation cost but also lacks consistency in improving machining due to density gradients in the components. In order to provide an effective solution in a cost-effective way, an easy-machinable version of stainless steel powder has been developed based on a modified powder manufacturing technology. Previous study has demonstrated that components made with the newly developed 300 series easy machinable stainless steel powder provide superior machinability in comparison with their standard grade counterparts. In this paper results obtained from evaluations of 400 series stainless steels will be presented. Machinability, material properties, and corrosion resistance of materials made with the newly developed 400 series easy machinable stainless steel powder will be compared with those of their standard grade counterparts.